Cho-Pats Patellar Stabilizer improves patellar tracking resulting in less knee degeneration, inflammation, and pain. It functions dynamically because the fabric-covered neoprene material applies constant pressure to the joint providing effective symptomatic relief of acute and chronic pain associated with patellar tendonitis, arthritis, and overuse syndromes. In addition, the Stabilizer has four enclosed firm plastic tubes acting as buttresses around the kneecap to reduce patellar subluxation and degeneration. The Patellar Stabilizer allows for full mobility of the knee joint while improving lateral and medial support for weak and arthritic knees. Sizing: Based On Mid-Kneecap Circumference, Indicate Left Or Right Knee. Note: If you are between sizes, we suggest you order the smaller size.